The invention relates to a belt tensioner for a generator belt drive of an internal combustion engine. The belt tensioner comprises one or more tensioning arms each with a tensioning roller supported on the arms and a tensioning spring applying a load on the tensioning arm or arms for pretensioning the belt and has a ring-shaped construction for mounting on the generator. In the assembled state of the belt drive, the belt tensioner encompasses the pulley of the generator and covers the belt in a plane that is spaced apart from the belt plane and runs on the other side of the belt plane with respect to the generator.
Such a belt tensioner with only one tensioning arm and accordingly one tensioning roller is known from EP 2 573 423 A1. A belt tensioner also according to the class with two tensioning arms and accordingly two tensioning rollers is known from DE 10 2013 102 562 A1.
In both cases, the belt plane runs axially between the circular ring-shaped tensioning arm bearing of the belt tensioner and the end face of the generator, so that, in the assembled state of the belt drive, the belt is covered by parts of the belt tensioner—in a view toward the belt plane and the generator. Thus, the belt assembly, i.e., installing the belt on the pulley of the generator, is not possible if the belt tensioner is already mounted on the generator. This obstacle can be disruptive both for the initial assembly of the belt drive and also when changing the belt for servicing reasons. This is because the generator and the belt tensioner cannot be delivered to the assembly line of the internal combustion engine as a preassembled structural unit without the belt. Conversely, there is the risk that the belt already placed on the pulley is in the way during the assembly of the belt tensioner on the generator. In addition, changing the belt requires the disassembly of the belt tensioner from the generator.